1. Field of the Invention
The present invention relates to a pyroelectric infrared detector; more particularly, the present invention relates to an improved infrared detector of the dual element type where the elements are connected in parallel but with opposite polarities.
2. Description of the Prior Art
U.S. Pat. 3,839,640 to Rossin discloses an infrared detector of the dual element type where the elements are connected in series but with opposite polarities. This detector has also a structural and manufacturing advantage in that the lead wires can be taken out from an electrode, which is mounted on one side of the pyroelectric materials, by means of a single operation. In addition, the device has excellent characteristics since various noise signals due to disturbances can be eliminated because of the fact that the dual elements are connected so as to have opposite polarities.
An example of a prior art detector of the dual element type where the elements are connected in parallel but with opposite polarities is shown in FIG. 1. However, this detector has a disadvantage in that four separate lead wires 4 must be taken out from electrodes 2a, 2b, 3a, 3b mounted on both sides of a pyroelectric material 1 and is thereby difficult to manufacture. Accordingly, it is necessary to taken out lead wires from only one side of a pyroelectric material in a fashion similar to the previously noted Rossin detector which has its elements connected in series but with opposite polarities in order to improve the manufacturability of a detector having its elements connected in parallel but with opposite polarities.
One prior art method cuts the central part (C) of said pyroelectric material 1 into two parts, one of the resulting two pieces being turned over and both pieces being bonded, so as to thereby reduce the number of lead wires by respectively taking out one lead wire from both sides of said pyroelectric material 1, as shown in FIG. 1. However, such a method cannot solve the previously noted problem in that lead wires cannot be taken out by a single operation because lead wires must be taken out from both sides of the pyroelectric material. In addition, the prior art method is equivalent to a configuration where two detectors of single element type construction are bonded opposite to each other in the direction thereof and thus has the disadvantage of an inferior balance of the element characteristics. Thus, it is necessary to mount all electrodes on a single pyroelectric material in order to improve the balance of the element characteristics.